What could be better than playing a crazy lady in a Harry Potter movie? Maybe playing a singing crazy lady in a new movie directed by your boyfriend — especially if he happens to be Tim Burton.

The director's new film version of the 1979 Broadway musical "Sweeney Todd" is a feast for the eyes and the ears — and a bloody great showcase for Helena Bonham Carter, who apparently had a ball getting all uglied up to star opposite Johnny Depp in one of her favorite musicals of all time.

MTV: You've wanted to play Mrs. Lovett since you were a teenager. Was it just because you wanted to shake some sense into her?

Helena Bonham Carter: [She laughs.] You know what? I just loved "Sweeney Todd," definitely. I did love the musical. I just love Stephen Sondheim. So, yeah, when I was 13, I guess I did. I went around in her hairdo. A friend of mine even used to call me Mrs. Lovett. That was my nickname! I was a strange child, I guess.

So when this part came, I just thought, 'She's such a fantastic part. She can be played so many different ways.' She'd been played in a pretty subversive way — I mean, Angela Lansbury played her in a specific way — but it really belonged onstage. So the opportunity to do her on film, when you can do just lots of other choices, I thought she could be a bit more clever than the way she'd previously been played. She could be. And Tim also, his whole vision of it was that he wanted both [Mrs. Lovett and Sweeney Todd] to be younger, so there was a bit of hope of a romance. And so I sort of thought, 'Well, I really want to bring out the fact that she's a woman, and a sensuous, sexual being, and her yearning and her love and adoration for this man who won't even notice her.'

MTV: The most she can hope for in her wildest fantasy is that he'll kind of put his hand on her leg, as he does during the song "By the Sea."

MTV: Sweeney Todd murders random innocent men in his quest for revenge, while she hides the bodies in her meat pies and serves them to unsuspecting customers. But Sweeney's need for revenge might not have been so bloody without her little lie. Do you think what she does is worse in a way?

Carter: In a way she is more reprehensible, yeah. But only because she loves him so much. She just can't bear to lose him, and that's why she lies. She is basically way more immoral, or amoral. She doesn't think twice about popping a body in a pie. Whereas he, you realize that he's really been just set off the deep end because of this horrible tragedy that's been dealt to him. ... But life was tough back then at the bottom of the pile in Victorian England. She's a tough, pragmatic survivor but really full of energy and zest and life.

MTV: How would you rate Mrs. Lovett against other villainesses you've played, such as, say, Bellatrix Lestrange from "Harry Potter"?

Carter: It's funny. It's like, the first thing you think when you get a baddie to play is that you stop thinking they're a baddie. You can't really play a baddie if you think you're a baddie. You just find a way in. Once you're inside, from their point of view, you can't judge yourself morally. I never thought she was a baddie. I had a huge amount of compassion and time for Mrs. Lovett.

MTV: Do you have compassion for Bellatrix?

Carter: For Bellatrix? Yeah. Anybody who tends to be a baddie or a psychotic, they tend to be damaged in a really fundamental way. There's a vulnerability, a deep vulnerability, a wound.

MTV: Both are in love with these really horrible men.

Carter: That's true, I hadn't thought about that. Men who really have no time for them and basically abuse them. Definitely an abusive relationship, yeah.